Tuyere block



Sept. 7, 1937. l w. v. McALLlsTER ET Al. 2,092,420

TUYRE BLOCK Filed Jan. 50, 1935 -PWLLJAMI/.YMLLJSTER LESLIE @Ko/WE Patented Sept. 7, 1937 UNITED STATES entre V"TUYRE BLOCK William V. McAllister and Leslie' (Ee/Korte, Detroit, Mich., assignors to Riley Stoker Corporation, Worcester, Mass., a corporation of Massachusetts Application January 30, 1935, Serial No. 4,133

5 Claims.

Y `This' invention relates to tuyre blocks, and moreparticularly to tuyre blocks for use 'in automatic stokers to support the fuel and distribute air thereto for combustion.

In automatic stokers of the underfeed type, it is customary to utilize rows of tuyre blocks located between the Stoker retorts, the blocks in each rowbeing arranged in an `overlapping or step-like formation to provide a tuyre structure Which slopes downwardly toward the rearof the furnace. In such a tuyre structure, the rear or nose portion of each tuyre block is exposed to contact with the fuel bed, Whereas the front or main body portion of the block is protected by the block thereabove. Even with the most careful operation, groups of tuyre blocks sometimes become overheated, perhaps as a result of thinspots in the fuel bed, and it becomes necessary toreplace the damaged blocks at considerable expense. It is of course necessary to shut down the furnace before such replacement can V12 heat much more rapidly than blocks of the usual construction. It has also been proposed to util ize-protecting caps ofrefractory material for the heat exposed portions of the blocks, but such caps are expensive andthey cannot satisfactorily withstand the combined effect of the heat, the chemical action of the ash from the fuel, and the abrasion of the fuel bed. While heat-resisting metals have been developed, tuyre blocks constructed from them are so expensive as to prevent any economic saving by their use.

It is accordingly the main object of the invention to overcome these difficulties and to provide `a tuyre block which will be relatively inexpensive to manufacture and which will have a useful life of service comparable to that obtainable with tuyre blocks constructed entirely of heat resisting metal.

With this and other objects in view, as will be apparent to those skilled in the art, the invention resides in the combination of parts set Aforthin the specification and covered by the claims appended hereto.

. Referring to the drawing illustrating one ernbodimentY of the-invention, and in which like reference numerals indicate like parts,

Fig. 1 is a perspective view of a tuyre block for an underfeed Stoker;

Fig. 2 is an elevation of a series of tuyre blocks assembled on a Stoker;

Fig. 3 is a top plan view of a mold for use in casting a tuyre block; and

Fig. Llis an elevation of the mold ready for the pouring operation, shown in partial section on the line 4 4 of Fig. 3.

The tuyre block illustrated in Fig. 1 is of the general type disclosed in the patent to Armour No. 1,896,569, granted February 7, 1933, and comprises a thin elongated flat substantially horizontal plate or web IB having spaced ribs il on its lower face forming air channels. A rectangular opening i2 is provided in the front portion of the web to reduce the resistance to the iiow of air through the blocks when assembled. Two anges Ill extend downwardly from opposite sides of the block at the front end thereof, the lower edges of these flanges sloping downwardly and rearwardly. A bolt hole i5 is provided in the web l0 in the rear of the opening i2.

The tuyre blocks are mounted in a step-like formation upon a downwardly and rearwardly sloping stoker` side-bar or retort side il, as shown in Fig. 2, with the flanges i4 engaging the upper surface of the side-bar. It will be understood that the side-bar is of hollow construction, as is customary, so that air may flow upwardly therethrough and escape to the fuel bed through the channels between the ribs l l.

It will be noted from Fig. 2 that only a comparatively small nose portion I9 at the rear end of each tuyre block is exposed to the fuel bed ithereabove, and that the main body portion of each tuyre block is protected by the next higher `block in the series. With blocks as heretofore constructed,v these nose portions have frequently becomeso damaged by the conditions encountered in serviceias to reduire replacement of the blocks at considerable expense. Attempts to solve the problem by providing separately replaceable nose portions of expensive heat-resisting metals have proven unsuccessful, and in our opinion this is due to the lack of sufcient heat transmission from the nose portion to the main body of the block.

In order to overcomethese difficulties, we construct the entire main body of the tuyre block of a comparatively cheap metal, such as ordinary cast iron, and we form the entire nose portion I9 of a suitable heat-resisting metal which is so joined to the main body as to ensure rapid heat transmission thereto. In the preferred embodiment the metal of the nose portion is integrally united with the metal of the body portion, and the junction between the two metals extends along a plane which slopes downwardly and rearwardly with respect to the web I0 of the block, as indicated by the dotted lines in Figs. 1 and 2. The integral union of the two metals over the substantial area represented by this inclined plane ensures the transmission of heat at a very rapid rate from the nose portion of the block to the comparatively cool main body portion, thus maintaining the nose portion at a temperature no higher than would be found in a homogeneous block under identical operating conditions. At the same time the inherent characteristics of the metal forming the nose portion enable it to withstand the operating conditions successfully. It will be noted that by sloping the junction plane downwardly toward the rear, we are able to obtain a relatively large area for the upper surface of the heat-resisting metal without requiring an excessive amount of this metal. In this way we use the costly material to the best advantage. It will be clear from Figs. 1 and 2 that the main body portion of the block is wedge shaped in longitudinal vertical section at its rear end, with the acute angle of the wedge at the bottom, and the nose portion IS is wedge shaped in longitudinal vertical section at its forward end with the acute angle of the wedge at the top, the sloping surfaces of the two wedge shaped portions being integrally united. l

By the term heat-resisting metal we do not necessarily mean a metal having a high melting point. In fact the metals which we consider best suited for our purpose probably melt at substantially the same temperature as ordinary cast iron. It is unusual for even the nose portion of a. stoker tuyre block to reach the melting point. The in-flowing air has sufcient cooling effect to prevent this under any normal operating conditions. The damage to tuyre blocks as heretofore constructed is we believe caused primarily by growth and oxidation. Growth of cast iron is a gradual permanent enlargement under the influence of heat, and particularly alternate heating and cooling. It greatly distorts and weakens the metal, and produces internal stresses which result in cracking and rapid disintegration of the block. Oxidation is of course a chemical combination of the metal with oxygen, a reaction which is greatly accelerated at high temperatures, causing scaling and wasting away of the metal. We are therefore primarily interested in a material which will remain comparatively free from growth and oxidation when exposed to high temperatures in an oxidizing atmosphere. It is a material of this nature to which we refer when we use the term heat-resisting metal.

Various heat-resisting metals may be utilized for our purposes. One suitable material is an alloyed cast iron, austeniticI in structure, and having an analysis as follows:

Per cent Total carbon 2. 75- 3. 10 Silicon 1. 2. 00

Nickel 12.00-15.00 Chromium 1. 50- 5. 00

Manganese 80- 1. 50 Copper 5. 00- 1.00

While an alloy of this type may be produced in a cupola, we much prefer to utilize an electric furnace, as it makes possible better control of the metal, a more uniform composition, and a higher pouring temperature.

In the manufacture of our improved tuyre block, we prepare a sand mold 2l having a mold cavity 22 of a shape corresponding to the desired shape of the tuyre block. This mold maybeproduced in the usual manner by means of a snapflask, which is removed after completion of the mold and a supporting metal jacket 23 substituted therefor. The mold 2| is preferably provided with two pouring basins 25 and 26, which communicate by means of gates 21 and 28 respectively with the cavity 22. Gate 21 leads to the portion of the cavity which corresponds to the main body of the tuyre block, and gate 28 leads to the portion of the cavity which corresponds to the nose portion of the block.

After completion of the mold it is tipped to a predetermined angle with the horizontal, with gate 28 higher than gate 21, and in order that the castings may be uniform we preferably mount each mold upon a wedge-shaped block 30 having an inclined upper surface, as shown in Fig. 4. With the mold in this position a suitable molten metal, such as ordinary cupola iron, is poured into the basin 25 and enters the cavity 22 through the gate 21. The pouring is continued until the metal reaches the level indicated by the broken line 32, at which time the metal Will i be about to overflow from the pouring basin 25. After an interval of time suflicient for the iron to cool slightly, the molten alloyed iron is poured at a comparatively high temperature into the basin 26 and flows through the gate 28 into the upper portion of the cavity 22 to form the nose of the tuyre block. If the time interval between the two pourings is correct, the two metals will not mix to any appreciable extent, and yet they will be fused together and integrally united along the junction plane. The proper interval for any particular design of tuyre block can be easily determined by trial. With the tuyre block illustrated, and a web ya of an inch in thickness, we have found that a time interval of approximately thirty seconds is satisfactory.

Because of the comparatively small quantity of alloyed iron required for the nose portion I9, the cost of the finished tuyre block will not greatly exceed the cost of the usual block constructed entirely of ordinary cast iron, and yet our improved block will have a useful life far exceeding that heretofore obtainable. This results from the ability of the metal of the nose portion to resist growth and oxidation at fairly high ternperatures, and the effect of the integral bond between the two metals in transferring heat at a rapid rate along the block, thus preventing the nose portion from reaching too high a temperature. we are able to obtain long life at a comparatively low cost.

Having thus described our invention, what we claim as new and desire to secure by Letters It is by combining these two factors that 2. A tuyre block comprising a front horizontally extending main` body portion formed of a' comparatively inexpensive metalv and wedge shaped at its rear end with the acute angle of the wedge at the bottom, and a rear horizon tally extending fuel supporting portion formed of a heat-resisting metal and wedge shaped at its forward end with the acute angle of the wedge at the top, the sloping surfaces of the two portions being integrally united to ensure rapid transmission of heat betweenv them.

3. A tuyre structure for a Stoker comprising a series of tuyreblocks piled in a downwardly and rearwardly sloping step-like formation with the rear end of each block exposed, the forward portion of each block being formed of a. comparatively inexpensive metal and the rear portion being formed of a heat-resisting metal, the two portions of each block being integrally united throughout a junction plane which extends from the upper surfacev of the block tothe lower surface thereof.

4. A tuyre structure for a stoker comprising a series of tuyre blocks piled in a downwardly 25 and rearwardly sloping step-like formation with portion of each block being formed of a heatresisting metal and wedge shaped in longitudinal vertical section at its forward end, and the forward portion of each block being formed of a comparatively inexpensive metal and wedge shaped in longitudinal Vertical Section at its rear end, the two portions of each block being integrally united throughout a junction plane i which is inclined from the horizontal.

5. A tuyre structure for a stoker comprising a series of tuyre blocks piled ina downwardly and rearwardly sloping step-like formation with the rear end of each block exposed, the rear portion of each block being formed` of a heat-resisting metal and wedge shaped in longitudinal Vertical section at its forward end with the acute angle of the wedge at the top, and the forward portion of each block being formed of a comparatively inexpensive metal and wedge shaped in longitudinal Vertical section at its rear end with the acute angle of the wedge at the'bottom, the two portions of eachr block being integrally united throughout a junction plane which is inclined downwardly and rearwardly.

WILLIAM V. MCALLIS'I'ER. LESLIE G. KORTE. 

